This invention relates to the art of horticulture and, more particularly, to products for controlling temperature, vapors and gases, weeds, light, nutrients and insects in the growing area.
Present-day horticulture techniques involve numerous complex and costly operations for augmenting such growth parameters as soil moisture and temperature, and for selectively controlling weeds, pest insects, plant virus, and fungus. For example, special surface layers, often formed of plastic and called mulches, are used to conserve moisture and to reduce erosion and leaching away of fertilizer. If they are light-impermeable, they also discourage weed growth; and if light-reflecting, they can augment foliage growth and control aphids and plant virus. If light-permeable, they can bring about rapid heating of the soil for early seed germination. Weed growth, in the case of transparent mulches, and ground insects, in the case of both transparent and opaque mulches, are typically controlled by herbicides and pesticides applied to the ground prior to mulching.
If all of the controls are properly coordinated and regulated, benefits in the form of improved yield and quality of the crop can be pronounced, although with attendant expense and in some cases risk. For example, the difficulty and hence cost of arranging sheet mulch over seed rows (either before or after planting) so that the sheet does not impede early growth and so that rain or sprinkler water can find its way to the plant roots, have limited the usefulness of this otherwise effective mulching technique. Also, the recovery of the sheet plastic after the crop harvest has been difficult. Corn stalks, for example, growing through tough plastic sheeting, render the sheet difficult to take up without wrapping up the stalks in a bulky, useless mass in which neither the plastic nor the stalks can be used. Also, ecological factors complicate the use of pesticides and herbicides. Migrating sprays, for example, can reach unintended areas, and lack of precision in metering can adversely affect the crop, in addition to creating possible long- and short-term contamination problems.
Planting beneath sheet mulches, whether clear or opaque, introduces the problem of the plants gaining access to the atmosphere through apertures in the sheet. At one extreme, with limited apertures, plant growth and watering are inhibited and excessive heat is generated; at the other, with many holes punched out of the sheet, the effectiveness of the mulch is lost by excessive soil exposure. If the seeds are planted before the sheet is put down, registration of the emergent plants and the apertures is difficult. Planting seeds through the sheets to overcome the registration problem is difficult and, in any event, it cannot readily be accomplished by conventional seeders.